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• Where to start with game development?

  - by steven_desu

  I asked this earlier in this thread at stackoverflow.com. One of the early comments redirected me here to gamedev.stackexchange.com, so I'm reposting here. Searching for related questions I found a number of very specific questions, but I'm afraid the specifics have proved fruitless for me and after 4 hours on Google I'm no closer than I started, so I felt reaching out to a community might be in order. First, my goal: I've never made a game before, although I've muddled over the possibility several times. I decided to finally sit down and start learning how to code games, use game engines, etc. All so that one day (hopefully soon) I'll be able to make functional (albeit simple) games. I can start adding complexity later, for now I'd be glad to have a keyboard-controlled camera moving in a 3D world with no interaction beyond that. My background: I've worked in SEVERAL programming languages ranging from PHP to C++ to Java to ASM. I'm not afraid of any challenges that come with learning the new syntax or limitations inherent in a new language. All of my past programming experience, however, has been strictly non-graphical and usually with little or extremely simple interaction during execution. I've created extensive and brilliant algorithms for solving logical and mathematical problems as well as graphing problems. However in every case input was either defined in a file, passed form an HTML form, or typed into the console. Real-time interaction with the user is something with which I have no experience. My question: Where should I start in trying to make games? Better yet- where should I start in trying to create a keyboard-navigable 3D environment? In searching online I've found several resources linking to game engines, graphics engines, and physics engines. Here's a brief summary of my experiences with a few engines I tried: Unreal SDK: The tutorial videos assume that you already have in-depth knowledge of 3D modeling, graphics engines, animations, etc. The "Getting Started" page offers no formal explanation of game development but jumps into how Unreal can streamline processes it assumes you're already familiar with. After downloading the SDK and launching it to see if the tools were as intuitive as they claimed, I was greeted with about 60 buttons and a blank void for my 3D modeling. Clicking on "add volume" (to attempt to add a basic cube) I was met with a menu of 30 options. Panicking, I closed the editor. Crystal Space: The website seemed rather informative, explaining that Crystal Space was just for graphics and the companion software, CEL, provided entity logic for making games. A demo game was provided, which was built using "CELStart", their simple tool for people with no knowledge of game programming. I launched the game to see what I might look forward to creating. It froze several times, the menus were buggy, there were thousands of graphical glitches, enemies didn't respond to damage, and when I closed the game it locked up. Gave up on that engine. IrrLicht: The tutorial assumes I have Visual Studio 6.0 (I have Visual Studio 2010). Following their instructions I was unable to properly import the library into Visual Studio and unable to call any of the functions that they kept using. Manually copying header files, class files, and DLLs into my project's folder - the project failed to properly compile. Clearly I'm not off to a good start and I'm going in circles. Can someone point me in the right direction? Should I start by downloading a program like Blender and learning 3D modeling, or should I be learning how to use a graphics engine? Should I look for an all-inclusive game engine, or is it better to try and code my own game logic? If anyone has actually made their own games, I would prefer to hear how they got their start. Also- taking classes at my school is not an option. Nothing is offered.

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• Where to start with game development?

  - by steven_desu

  Searching for related questions I found a number of very specific questions, but I'm afraid the specifics have proved fruitless for me and after 4 hours on Google I'm no closer than I started, so I felt reaching out to a community might be in order. First, my goal: I've never made a game before, although I've muddled over the possibility several times. I decided to finally sit down and start learning how to code games, use game engines, etc. All so that one day (hopefully soon) I'll be able to make functional (albeit simple) games. I can start adding complexity later, for now I'd be glad to have a keyboard-controlled camera moving in a 3D world with no interaction beyond that. My background: I've worked in SEVERAL programming languages ranging from PHP to C++ to Java to ASM. I'm not afraid of any challenges that come with learning the new syntax or limitations inherent in a new language. All of my past programming experience, however, has been strictly non-graphical and usually with little or extremely simple interaction during execution. I've created extensive and brilliant algorithms for solving logical and mathematical problems. However in every case input was either defined in a file, passed form an HTML form, or typed into the console. Real-time interaction with the user is something with which I have no experience. My question: Where should I start in trying to make games? Better yet- where should I start in trying to create a keyboard-navigable 3D environment? In searching online I've found several resources linking to game engines, graphics engines, and physics engines. Here's a brief summary of my experiences with a few engines I tried: Unreal SDK: The tutorial videos assume that you already have in-depth knowledge of 3D modeling, graphics engines, animations, etc. The "Getting Started" page offers no formal explanation of game development but jumps into how Unreal can streamline processes it assumes you're already familiar with. After downloading the SDK and launching it to see if the tools were as intuitive as they claimed, I was greeted with about 60 buttons and a blank void for my 3D modeling. Clicking on "add volume" (to attempt to add a basic cube) I was met with a menu of 30 options. Panicking, I closed the editor. Crystal Space: The website seemed rather informative, explaining that Crystal Space was just for graphics and the companion software, CEL, provided entity logic for making games. A demo game was provided, which was built using "CELStart", their simple tool for people with no knowledge of game programming. I launched the game to see what I might look forward to creating. It froze several times, the menus were buggy, there were thousands of graphical glitches, enemies didn't respond to damage, and when I closed the game it locked up. Gave up on that engine. IrrLicht: The tutorial assumes I have Visual Studio 6.0 (I have Visual Studio 2010). Following their instructions I was unable to properly import the library into Visual Studio and unable to call any of the functions that they kept using. Manually copying header files, class files, and DLLs into my project's folder - the project failed to properly compile. Clearly I'm not off to a good start and I'm going in circles. Can someone point me in the right direction? Should I start by downloading a program like Blender and learning 3D modeling, or should I be learning how to use a graphics engine? Should I look for an all-inclusive game engine, or is it better to try and code my own game logic? If anyone has actually made their own games, I would prefer to hear how they got their start. Also- taking classes at my school is not an option. Nothing is offered.

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• Using the Script Component as a Conditional Split

  This is a quick walk through on how you can use the Script Component to perform Conditional Split like behaviour, splitting your data across multiple outputs. We will use C# code to decide what does flows to which output, rather than the expression syntax of the Conditional Split transformation. Start by setting up the source. For my example the source is a list of SQL objects from sys.objects, just a quick way to get some data: SELECT type, name FROM sys.objects type name S syssoftobjrefs F FK_Message_Page U Conference IT queue_messages_23007163 Shown above is a small sample of the data you could expect to see. Once you have setup your source, add the Script Component, selecting Transformation when prompted for the type, and connect it up to the source. Now open the component, but don’t dive into the script just yet. First we need to select some columns. Select the Input Columns page and then select the columns we want to uses as part of our filter logic. You don’t need to choose columns that you may want later, this is just the columns used in the script itself. Next we need to add our outputs. Select the Inputs and Outputs page.You get one by default, but we need to add some more, it wouldn’t be much of a split otherwise. For this example we’ll add just one more. Click the Add Output button, and you’ll see a new output is added. Now we need to set some properties, so make sure our new Output 1 is selected. In the properties grid change the SynchronousInputID property to be our input Input 0, and  change the ExclusionGroup property to 1. Now select Ouput 0 and change the ExclusionGroup property to 2. This value itself isn’t important, provided each output has a different value other than zero. By setting this property on both outputs it allows us to split the data down one or the other, making each exclusive. If we left it to 0, that output would get all the rows. It can be a useful feature allowing you to copy selected rows to one output whilst retraining the full set of data in the other. Now we can go back to the Script page and start writing some code. For the example we will do a very simple test, if the value of the type column is U, for user table, then it goes down the first output, otherwise it ends up in the other. This mimics the exclusive behaviour of the conditional split transformation. public override void Input0_ProcessInputRow(Input0Buffer Row) { // Filter all user tables to the first output, // the remaining objects down the other if (Row.type.Trim() == "U") { Row.DirectRowToOutput0(); } else { Row.DirectRowToOutput1(); } } The code itself is very simple, a basic if clause that determines which of the DirectRowToOutput methods we call, there is one for each output. Of course you could write a lot more code to implement some very complex logic, but the final direction is still just a method call. If we now close the script component, we can hook up the outputs and test the package. Your numbers will vary depending on the sample database but as you can see we have clearly split out input data into two outputs. As a final tip, when adding the outputs I would normally rename them, changing the Name in the Properties grid. This means the generated methods follow the pattern as do the path label shown on the design surface, making everything that much easier to recognise.

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• How does interpolation actually work to smooth out an object's movement?

  - by user22241

  I've asked a few similar questions over the past 8 months or so with no real joy, so I am going make the question more general. I have an Android game which is OpenGL ES 2.0. within it I have the following Game Loop: My loop works on a fixed time step principle (dt = 1 / ticksPerSecond) loops=0; while(System.currentTimeMillis() > nextGameTick && loops < maxFrameskip){ updateLogic(dt); nextGameTick+=skipTicks; timeCorrection += (1000d/ticksPerSecond) % 1; nextGameTick+=timeCorrection; timeCorrection %=1; loops++; } render(); My intergration works like this: sprite.posX+=sprite.xVel*dt; sprite.posXDrawAt=sprite.posX*width; Now, everything works pretty much as I would like. I can specify that I would like an object to move across a certain distance (screen width say) in 2.5 seconds and it will do just that. Also because of the frame skipping that I allow in my game loop, I can do this on pretty much any device and it will always take 2.5 seconds. Problem However, the problem is that when a render frame skips, the graphic stutter. It's extremely annoying. If I remove the ability to skip frames, then everything is smooth as you like, but will run at different speeds on different devices. So it's not an option. I'm still not sure why the frame skips, but I would like to point out that this is Nothing to do with poor performance, I've taken the code right back to 1 tiny sprite and no logic (apart from the logic required to move the sprite) and I still get skipped frames. And this is on a Google Nexus 10 tablet (and as mentioned above, I need frame skipping to keep the speed consistent across devices anyway). So, the only other option I have is to use interpolation (or extrapolation), I've read every article there is out there but none have really helped me to understand how it works and all of my attempted implementations have failed. Using one method I was able to get things moving smoothly but it was unworkable because it messed up my collision. I can foresee the same issue with any similar method because the interpolation is passed to (and acted upon within) the rendering method - at render time. So if Collision corrects position (character now standing right next to wall), then the renderer can alter it's position and draw it in the wall. So I'm really confused. People have said that you should never alter an object's position from within the rendering method, but all of the examples online show this. So I'm asking for a push in the right direction, please do not link to the popular game loop articles (deWitters, Fix your timestep, etc) as I've read these multiple times. I'm not asking anyone to write my code for me. Just explain please in simple terms how Interpolation actually works with some examples. I will then go and try to integrate any ideas into my code and will ask more specific questions if need-be further down the line. (I'm sure this is a problem many people struggle with).

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• Walkthrough: Scheduling jobs using Quartz.net &ndash; Part 1: What is Quartz.Net?

  - by Tarun Arora

  Quartz.NET is a full-featured, open source enterprise job scheduling system written in .NET platform that can be used from smallest apps to large scale enterprise systems. What is the problem that we trying to address? I want to schedule the execution of a task but only when something happens. Let’s call that something a trigger, so... if the trigger is met => execute the task. Sounds simple, why not use windows task scheduler for this? Well, windows task scheduler is great for tasks where the trigger can be easily defined. With windows task scheduler will you be able to schedule a task to run on every working day according to the UK calendar (exclude all weekends & bank holidays) without either writing the logic for day check in the task or a wrapper script calling into the task. The task should just contain the execution logic and should not have anything to do with the schedule for execution; Quartz.net allows you to achieve this and lots more. A quartz.net trigger gives you the flexibility for task invocation based on the following triggers, 1. at a certain time of day (to the millisecond) 2. on certain days of the week 3. on certain days of the month 4. on certain days of the year 5. not on certain days listed within a registered Calendar (such as business holidays) 6. repeated a specific number of times 7. repeated until a specific time/date 8. repeated indefinitely 9. repeated with a delay interval Did 8 – repeat indefinitely just ring a bell? I’ll be covering that in the future post. Using Quartz.net as a windows service You can have Quartz.net run as a standalone instance within its own .NET virtual machine instance via .NET Remoting. Let’s take a look at typical application architecture. In the figure below, I have the application tier set up on Machine 1, database set up on Machine 2 and Quartz.net set up on Machine 3 which is normally the architecture for most (if not all) enterprise applications. Figure 1 -  Typical Application architecture while using Quartz.net as a windows service What other options do I have if I don’t want to use Quartz.net? Quartz.net is just one of the many job scheduling services. Have a look at this comprehensive list of free and paid enterprise job scheduling software along with their feature comparison. http://en.wikipedia.org/wiki/List_of_job_scheduler_software This was first in the series of posts on enterprise scheduling using Quartz.net, in the next post I’ll be covering how to Install Quartz.net as a windows service. Thank you for taking the time out and reading this blog post. If you enjoyed the post, remember to subscribe to http://feeds.feedburner.com/TarunArora. Stay tuned!

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• Extrapolation breaks collision detection

  - by user22241

  Before applying extrapolation to my sprite's movement, my collision worked perfectly. However, after applying extrapolation to my sprite's movement (to smooth things out), the collision no longer works. This is how things worked before extrapolation: However, after I implement my extrapolation, the collision routine breaks. I am assuming this is because it is acting upon the new coordinate that has been produced by the extrapolation routine (which is situated in my render call ). After I apply my extrapolation How to correct this behaviour? I've tried puting an extra collision check just after extrapolation - this does seem to clear up a lot of the problems but I've ruled this out because putting logic into my rendering is out of the question. I've also tried making a copy of the spritesX position, extrapolating that and drawing using that rather than the original, thus leaving the original intact for the logic to pick up on - this seems a better option, but it still produces some weird effects when colliding with walls. I'm pretty sure this also isn't the correct way to deal with this. I've found a couple of similar questions on here but the answers haven't helped me. This is my extrapolation code: public void onDrawFrame(GL10 gl) { //Set/Re-set loop back to 0 to start counting again loops=0; while(System.currentTimeMillis() > nextGameTick && loops < maxFrameskip){ SceneManager.getInstance().getCurrentScene().updateLogic(); nextGameTick+=skipTicks; timeCorrection += (1000d/ticksPerSecond) % 1; nextGameTick+=timeCorrection; timeCorrection %=1; loops++; tics++; } extrapolation = (float)(System.currentTimeMillis() + skipTicks - nextGameTick) / (float)skipTicks; render(extrapolation); } Applying extrapolation render(float extrapolation){ //This example shows extrapolation for X axis only. Y position (spriteScreenY is assumed to be valid) extrapolatedPosX = spriteGridX+(SpriteXVelocity*dt)*extrapolation; spriteScreenPosX = extrapolationPosX * screenWidth; drawSprite(spriteScreenX, spriteScreenY); } Edit As I mentioned above, I have tried making a copy of the sprite's coordinates specifically to draw with.... this has it's own problems. Firstly, regardless of the copying, when the sprite is moving, it's super-smooth, when it stops, it's wobbling slightly left/right - as it's still extrapolating it's position based on the time. Is this normal behavior and can we 'turn it off' when the sprite stops? I've tried having flags for left / right and only extrapolating if either of these is enabled. I've also tried copying the last and current positions to see if there is any difference. However, as far as collision goes, these don't help. If the user is pressing say, the right button and the sprite is moving right, when it hits a wall, if the user continues to hold the right button down, the sprite will keep animating to the right, while being stopped by the wall (therefore not actually moving), however because the right flag is still set and also because the collision routine is constantly moving the sprite out of the wall, it still appear to the code (not the player) that the sprite is still moving, and therefore extrapolation continues. So what the player would see, is the sprite 'static' (yes, it's animating, but it's not actually moving across the screen), and every now and then it shakes violently as the extrapolation attempts to do it's thing....... Hope this help

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• The battle between Java vs. C#

  The battle between Java vs. C# has been a big debate amongst the development community over the last few years. Both languages have specific pros and cons based on the needs of a particular project. In general both languages utilize a similar coding syntax that is based on C++, and offer developers similar functionality. This being said, the communities supporting each of these languages are very different. The divide amongst the communities is much like the political divide in America, where the Java community would represent the Democrats and the .Net community would represent the Republicans. The Democratic Party is a proponent of the working class and the general population. Currently, Java is deeply entrenched in the open source community that is distributed freely to anyone who has an interest in using it. Open source communities rely on developers to keep it alive by constantly contributing code to make applications better; essentially they develop code by the community. This is in stark contrast to the C# community that is typically a pay to play community meaning that you must pay for code that you want to use because it is developed as products to be marketed and sold for a profit. This ties back into my reference to the Republicans because they typically represent the needs of business and personal responsibility. This is emphasized by the belief that code is a commodity and that it can be sold for a profit which is in direct conflict to the laissez-faire beliefs of the open source community. Beyond the general differences between Java and C#, they also target two different environments. Java is developed to be environment independent and only requires that users have a Java virtual machine running in order for the java code to execute. C# on the other hand typically targets any system running a windows operating system and has the appropriate version of the .Net Framework installed. However, recently there has been push by a segment of the Open source community based around the Mono project that lets C# code run on other non-windows operating systems. In addition, another feature of C# is that it compiles into an intermediate language, and this is what is executed when the program runs. Because C# is reduced down to an intermediate language called Common Language Runtime (CLR) it can be combined with other languages that are also compiled in to the CLR like Visual Basic (VB) .Net, and F#. The allowance and interaction between multiple languages in the .Net Framework enables projects to utilize existing code bases regardless of the actual syntax because they can be compiled in to CLR and executed as one codebase. As a software engineer I personally feel that it is really important to learn as many languages as you can or at least be open to learn as many languages as you can because no one language will work in every situation.  In some cases Java may be a better choice for a project and others may be C#. It really depends on the requirements of a project and the time constraints. In addition, I feel that is really important to concentrate on understanding the logic of programming and be able to translate business requirements into technical requirements. If you can understand both programming logic and business requirements then deciding which language to use is just basically choosing what syntax to write for a given business problem or need. In regards to code refactoring and dynamic languages it really does not matter. Eventually all projects will be refactored or decommissioned to allow for progress. This is the way of life in the software development industry. The language of a project should not be chosen based on the fact that a project will eventually be refactored because they all will get refactored.

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• PowerShell and SMO – be careful how you iterate

  - by Fatherjack

  I’ve yet to have a totally smooth experience with PowerShell and it was late on Friday when I crashed into this problem. I haven’t investigated if this is a generally well understood circumstance and if it is then I apologise for repeating everything. Scenario: I wanted to scan a number of server for many properties, including existing logins and to identify which accounts are bestowed with sysadmin privileges. A great task to pass to PowerShell, so with a heavy heart I started up PowerShellISE and started typing. The script doesn’t come easily to me but I follow the logic of SMO and the properties and methods available with the language so it seemed something I should be able to master. Version #1 of my script. And the results it returns when executed against my home laptop server. These results looked good and for a long time I was concerned with other parts of the script, for all intents and purposes quite happy that this was an accurate assessment of the server. Let’s just review my logic for each step of the code at the top. Lines 1 to 7 just set up our variables and write out the header message Line 8 our first loop, to go through each login on the server Line 10 an inner loop that will assess each role name that each login has been assigned Line 11 a test to see if each role has the name ‘sysadmin’ Line 13 write out the login name with a bright format as it is a sysadmin login Line 17 write out the login name with no formatting It is quite possible that here someone with more PowerShell experience than me will be shouting at their screen pointing at the error I made but to me this made total sense. Until I altered the code, I altered lines 6 and 7 of code above to be: $c = $Svr.Logins.Count write-host “There are $c Logins on the server” This changed my output to look like this: This started alarm bells ringing – there are clearly not 13 logins listed So, let’s see where things are going wrong, edit the script so it looks like this. I’ve highlighted the changes to make Running this code shows me these results Our $n variable should count up by one for each login returned and We are clearly missing some logins. I referenced this list back to Management Studio for my server and see the Logins as below, where there are clearly 13 logins. We see a Login called Annette in SSMS but not in the script results so I opened that up and looked at its properties and it’s server roles in particular. The account has only public access to the server. Inspection of the other logins that the PowerShell script misses out show they too are only members of the public role. Right now I can’t work out whether there is a good reason for this and if it should be expected behaviour or not. Please spend a few minutes to leave a comment if you have an opinion or theory for this. How to get the full list of logins. Clearly I needed to get a full list of the logins so set about reviewing my code to see if there was a better way to iterate through the roles for each login. This is the code that I came up with and I think it is doing everything that I need it to. It gives me the expected results like this: So it seems that the ListMembers() method is the trouble maker in my first versions of the code. I would have expected that ListMembers should return Logins that are only members of the public role, certainly Technet makes no reference to it being left out in it’s Login.ListMembers details. Suffice to say, it’s a lesson learned and I will approach using it with caution in future circumstances.

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• How to place rooms proceduraly (rule based) on in a game word

  - by gardian06

  I am trying to design the algorithm for my level generation which is a rule driven system. I have created all the rules for the system. I have taken care to insure that all rooms make sense in a grid type setup. for example: these rooms could make this configuration The logic flow code that I have so far Door{ Vector3 position; POD orient; // 5 possible values (up is not an option) bool Open; } Room{ String roomRule; Vector3 roomPos; Vector3 dimensions; POD roomOrient; // 4 possible values List doors<Door>; } LevelManager{ float scale = 18f; List usedRooms<Room>; List openDoors<Door> bool Grid[][][]; Room CreateRoom(String rule, Vector3 position, POD Orient){ place recieved values based on rule fill in other data } Vector3 getDimenstions(String rule){ return dimensions of the room } RotateRoom(POD rotateAmount){ rotate all items in the room } MoveRoom(Room toBeMoved, POD orientataion, float distance){ move the position of the room based on inputs } GenerateMap(Vector3 size, Vector3 start, Vector3 end){ Grid = array[size.y][size.x][size.z]; Room floatingRoom; floatingRoom = Room.CreateRoom(S01, start, rand(4)); usedRooms.Add(floatingRoom); for each Door in floatingRoom.doors{ openDoors.Add(door); } // fill used grid spaces floatingRoom = Room.CreateRoom(S02, end, rand(4); usedRooms.Add(floatingRoom); for each Door in floatingRoom.doors{ openDoors.Add(door); } Vector3 nRoomLocation; Door workingDoor; string workingRoom; // fill used grid spaces // pick random door on the openDoors list workingDoor = /*randomDoor*/ // get a random rule nRoomLocation = workingDoor.position; // then I'm lost } } I know that I have to make sure for convergence (namely the end is reachable), and to do this until there are no more doors on the openDoors list. right now I am simply trying to get this to work in 2D (there are rules that introduce 3D), but I am working on a presumption that a rigorous algorithm can be trivially extended to 3D. EDIT: my thought pattern so far is to take an existing open door and then pick a random room (restrictions can be put in later) place that room's center at the doors location move the room in the direction of the doors orientation half the rooms dimension w/respect to that axis then test against the 3D array to see if all the grid points are open, or have been used, or if there is even space to put the room (caseEdge) if caseEdge (which can also occur in between rooms) then put the door on a toBeClosed list, and remove it from the open list (placing a wall or something there). then to do some kind of test that both the start, and the goal are connected, and reachable from each other (each room has nodes for AI, but I don't want to "have" to pull those out to accomplish this). but this logic has the problem for say the U, or L shaped rooms in my example, and then I also have a problem conceptually if the room needs to be rotated.

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• Appropriate design / technologies to handle dynamic string formatting?

  - by Mark W

  recently I was tasked with implementing a way of adding support for versioning of hardware packet specifications to one of our libraries. First a bit of information about the project. We have a hardware library which has classes for each of the various commands we support sending to our hardware. These hardware modules are essentially just lights with a few buttons, and a 2 or 4 digit display. The packets typically follow the format {SOH}AADD{ETX}, where AA is our sentinel action code, and DD is the device ID. These packet specs are different from one command to the next obviously, and the different firmware versions we have support different specifications. For example, on version 1 an action code of 14 may have a spec of {SOH}AADDTEXT{ETX} which would be AA = 14 literal, DD = device ID, TEXT = literal text to display on the device. Then we come out with a revision with adds an extended byte(s) onto the end of the packet like this {SOH}AADDTEXTE{ETX}. Assume the TEXT field is fixed width for this example. We have now added a new field onto the end which could be used to say specify the color or flash rate of the text/buttons. Currently this java library only supports one version of the commands, the latest. In our hardware library we would have a class for this command, say a DisplayTextArgs.java. That class would have fields for the device ID, the text, and the extended byte. The command class would expose a method which generates the string ("{SOH}AADDTEXTE{ETX}") using the value from the class. In practice we would create the Args class as needed, populate the fields, call the method to get our packet string, then ship that down across the CAN. Some of our other commands specification can vary for the same command, on the same version, depending on some runtime state. For example, another command for version 1 may be {SOH}AA{ETX}, where this action code clears all of the modules behind a specific controller device of their text. We may overload this packet to have option fields with multiple meanings like {SOH}AAOC{ETX} where OC is literal text, which tells the controller to only clear text on a specific module type, and to leave the others alone, or the spec could also have an option format of {SOH}AADD{ETX} to clear the text off a a specific device. Currently, in the method which generates the packet string, we would evaluate fields on the args class to determine which spec we will be using when formatting the packet. For this example, it would be along the lines of: if m_DeviceID != null then use {SOH}AADD{ETX} else if m_ClearOCs == true then use {SOH}AAOC{EXT} else use {SOH}AA{ETX} I had considered using XML, or a database to store String.format format strings, which were linked to firmware version numbers in some table. We would load them up at startup, and pass in the version number of the hardwares firmware we are currently using (I can query the devices for their firmware version, but the version is not included in all packets as part of the spec). This breaks down pretty quickly because of the dynamic nature of how we select which version of the command to use. I then considered using a rule engine to possibly build out expressions which could be interpreted at runtume, to evaluate the args class's state, and from that select the appropriate format string to use, but my brief look at rule engines for java scared me away with its complexity. While it seems like it might be a viable solution, it seems overly complex. So this is why I am here. I wouldn't say design is my strongest skill, and im having trouble figuring out the best way to approach this problem. I probably wont be able to radically change the args classes, but if the trade off was good enough, I may be able to convince my boss that the change is appropriate. What I would like from the community is some feedback on some best practices / design methodologies / API or other resources which I could use to accomplish: Logic to determine which set of commands to use for a given firmware version Of those command, which version of each command to use (based on the args classes state) Keep the rules logic decoupled from the application so as to avoid needing releases for every firmware version Be simple enough so I don't need weeks of study and trial and error to implement effectively.

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• Is there any kind of established architecture for browser based games?

  - by black_puppydog

  I am beginning the development of a broser based game in which players take certain actions at any point in time. Big parts of gameplay will be happening in real life and just have to be entered into the system. I believe a good kind of comparison might be a platform for managing fantasy football, although I have virtually no experience playing that, so please correct me if I am mistaken here. The point is that some events happen in the program (i.e. on the server, out of reach for the players) like pulling new results from some datasource, starting of a new round by a game master and such. Other events happen in real life (two players closing a deal on the transfer of some team member or whatnot - again: have never played fantasy football) and have to be entered into the system. The first part is pretty easy since the game masters will be "staff" and thus can be trusted to a certain degree to not mess with the system. But the second part bothers me quite a lot, especially since the actions may involve multiple steps and interactions with different players, like registering a deal with the system that then has to be approved by the other party or denied and passed on to a game master to decide. I would of course like to separate the game logic as far as possible from the presentation and basic form validation but am unsure how to do this in a clean fashion. Of course I could (and will) put some effort into making my own architectural decisions and prototype different ideas. But I am bound to make some stupid mistakes at some point, so I would like to avoid some of that by getting a little "book smart" beforehand. So the question is: Is there any kind of architectural works that I can read up on? Papers, blogs, maybe design documents or even source code? Writing this down this seems more like a business application with business rules, workflows and such... Any good entry points for that? EDIT: After reading the first answers I am under the impression of having made a mistake when including the "MMO" part into the title. The game will not be all fancy (i.e. 3D or such) on the client side and the logic will completely exist on the server. That is, apart from basic form validation for the user which will also be mirrored on the server side. So the target toolset will be HTML5, JavaScript, probably JQuery(UI). My question is more related to the software architecture/design of a system that enforces certain rules. Separation of ruleset and presentation One problem I am having is that I want to separate the game rules from the presentation. The first step would be to make an own module for the game "engine" that only exposes an interface that allows all actions to be taken in a clean way. If an action fails with regard to some pre/post condition, the engine throws an exception which is then presented to the user like "you cannot sell something you do not own" or "after that you would end up in a situation which is not a valid game state." The problem here is that I would like to be able to not even present invalid action in the first place or grey out the corresponding UI elements. Changing and tweaking the ruleset Another big thing is the ruleset. It will probably evolve over time and most definitely must be tweaked. What's more, it should be possible (to a certain extent) to build a ruleset that fits a specific game round, i.e. choosing different kinds of behaviours in different aspects of the game. This would do something like "we play it with extension A today but we throw out extension B." For me, this screams "Architectural/Design pattern" but I have no idea on who might have published on something like this, not even what to google for.

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• DRY Validation with MVC2

  - by Matthew

  Hi All, I'm trying to figure out how I can define validation rules for my domain objects in one single location within my application but have run in to a snag... Some background: My location has several parts: - Database - DAL - Business Logic Layer - SOAP API Layer - MVC website The MVC website accesses the database via the SOAP API, just as third parties would. We are using server and and client side validation on the MVC website as well as in the SOAP API Layer. To avoid having to manually write client side validation we are implementing strongly typed views in conjunction with the Html.TextBoxFor and Html.ValidationMessageFor HTML helpers, as shown in Step 3 here. We also create custom models for each form where one form takes input for multiple domain objects. This is where the problem begins, the HTML helpers read from the model for the data annotation validation attributes. In most cases our forms deal with multiple domain objects and you can't specify more than one type in the <%@Page ... Inherits="System.Web.Mvc.ViewPage" % page directive. So we are forced to create a custom model class, which would mean duplicating validation attributes from the domain objects on to the model class. I've spent quite some time looking for workarounds to this, such has referencing the same MetadataType from both the domain class and the custom MVC models, but that won't work for several reasons: You can only specify one MetadataType attribute per class, so its a problem if a model references multiple domain objects, each with their own metadata type. The data annotation validation code throws an exception if the model class doesn't contain a property that is specified in the referenced MetadataType which is a problem with the model only deals with a subset of the properties for a given domain object. I've looked at other solutions as well but to no avail. If anyone has any ideas on how to achieve a single source for validation logic that would work across MVC client and server side validation functionality and other locations (such as my SOAP API) I would love to hear it! Thanks in advance, Matthew

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• Entity Framework 4 Code First and the new() Operator

  - by Eric J.

  I have a rather deep hierarchy of objects that I'm trying to persist with Entity Framework 4, POCO, PI (Persistence Ignorance) and Code First. Suddenly things started working pretty well when it dawned on me to not use the new() operator. As originally written, the objects frequently use new() to create child objects. Instead I'm using my take on the Repository Pattern to create all child objects as needed. For example, given: class Adam { List<Child> children; void AddChildGivenInput(string input) { children.Add(new Child(...)); } } class Child { List<GrandChild> grandchildren; void AddGrandChildGivenInput(string input) { grandchildren.Add(new GrandChild(...)); } } class GrandChild { } ("GivenInput" implies some processing not shown here) I define an AdamRepository like: class AdamRepository { Adam Add() { return objectContext.Create<Adam>(); } Child AddChildGivenInput(Adam adam, string input) { return adam.children.Add(new Child(...)); } GrandChild AddGrandchildGivenInput(Child child, string input) { return child.grandchildren.Add(new GrandChild(...)); } } Now, this works well enough. However, I'm no longer "ignorant" of my persistence mechanism as I have abandoned the new() operator. Additionally, I'm at risk of an anemic domain model since so much logic ends up in the repository rather than in the domain objects. After much adieu, a question: Or rather several questions... Is this pattern required to work with EF 4 Code First? Is there a way to retain use of new() and still work with EF 4 / POCO / Code First? Is there another pattern that would leave logic in the domain object and still work with EF 4 / POCO / Code First? Will this restriction be lifted in later versions of Code First support? Sometimes trying to go the POCO / Persistence Ignorance route feels like swimming upstream, other times it feels like swimming up Niagra Falls.

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• Mapping and metadata information could not be found for EntityType Exception

  - by dcompiled

  I am trying out ASP.NET MVC Framework 2 with the Microsoft Entity Framework and when I try and save new records I get this error: Mapping and metadata information could not be found for EntityType 'WebUI.Controllers.PersonViewModel' My Entity Framework container stores records of type Person and my view is strongly typed with class PersonViewModel which derives from Person. Records would save properly until I tried to use the derived view model class. Can anyone explain why the metadata class doesnt work when I derive my view model? I want to be able to use a strongly typed model and also use data annotations (metadata) without resorting to mixing my storage logic (EF classes) and presentation logic (views). // Rest of the Person class is autogenerated by the EF [MetadataType(typeof(Person.Metadata))] public partial class Person { public sealed class Metadata { [DisplayName("First Name")] [Required(ErrorMessage = "Field [First Name] is required")] public object FirstName { get; set; } [DisplayName("Middle Name")] public object MiddleName { get; set; } [DisplayName("Last Name")] [Required(ErrorMessage = "Field [Last Name] is required")] public object LastName { get; set; } } } // From the View (PersonCreate.aspx) <%@ Page Language="C#" MasterPageFile="~/Views/Shared/Site.Master" Inherits="System.Web.Mvc.ViewPage<WebUI.Controllers.PersonViewModel>" %> // From PersonController.cs public class PersonViewModel : Person { public List<SelectListItem> TitleList { get; set; } } // end class PersonViewModel

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• serializing type definitions?

  - by Dave

  I'm not positive I'm going about this the right way. I've got a suite of applications that have varying types of output (custom defined types). For example, I might have a type called Widget: Class Widget Public name as String End Class Throughout the course of operation, when a user experiences a certain condition, the application will take that output instance of widget that user received, serialize it, and log it to the database noting the name of the type. Now, I have other applications that do something similar, but instead of dealing with Widget, it could be some totally random other type with different attributes, but again I serialize the instance, log it to the db, and note the name of the type. I have maybe a half dozen different types and don't anticipate too many additional ones in the future. After all this is said and done, I have an admin interface that looks through these logs, and has the ability for the user to view the contents of this data thats been logged. The Admin app has a reference to all the types involved, and with some basic switch case logic hinged upon the name of the type, will cast it into their original types, and pass it on to some handlers that have basic display logic to spit the data back out in a readable format (one display handler for each type) NOW... all this is well and good... Until one day, my model changed. The Widget class now has deprecated the name attribute and added on a bunch of other attributes. I will of course get type mismatches in the admin side when I try to reconstitute this data. I was wondering if there was some way, at runtime, i could perhaps reflect through my code and get a snapshot of the type definition at that precise moment, serialize it, and store it along with the data so that I could somehow use this to reconstitute it in the future?

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• Notifying view controller when subview touch events occur.

  - by Nebs

  I have a UIViewController whose view has a custom subview. This custom subview needs to track touch events and report swipe gestures. Currently I put touchesBegan, touchesMoved, touchesEnded and touchesCancelled in the subview class. With some extra logic I am able to get swipe gestures and call my handleRightSwipe and handleLeftSwipe methods. So now when I swipe within the subview it calls its local swipe handling methods. This all works fine. But what I really need is for the handleRightSwipe and handleLeftSwipe methods to be in the view controller. I could leave them in the subview class but then I'd have to bring in all the logic and data as well and that kind of breaks the MVC idea. So my question is is there a clean way to handle this? Essentially I want to keep my touch event methods in the subview so that they only trigger for that specific view. But I also want the view controller to be informed when these touch events (or in this case swipe gestures) occur. Any ideas? Thanks.

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• Why use short-circuit code?

  - by Tim Lytle

  Related Questions: Benefits of using short-circuit evaluation, Why would a language NOT use Short-circuit evaluation?, Can someone explain this line of code please? (Logic & Assignment operators) There are questions about the benefits of a language using short-circuit code, but I'm wondering what are the benefits for a programmer? Is it just that it can make code a little more concise? Or are there performance reasons? I'm not asking about situations where two entities need to be evaluated anyway, for example: if($user->auth() AND $model->valid()){ $model->save(); } To me the reasoning there is clear - since both need to be true, you can skip the more costly model validation if the user can't save the data. This also has a (to me) obvious purpose: if(is_string($userid) AND strlen($userid) > 10){ //do something }; Because it wouldn't be wise to call strlen() with a non-string value. What I'm wondering about is the use of short-circuit code when it doesn't effect any other statements. For example, from the Zend Application default index page: defined('APPLICATION_PATH') || define('APPLICATION_PATH', realpath(dirname(__FILE__) . '/../application')); This could have been: if(!defined('APPLICATION_PATH')){ define('APPLICATION_PATH', realpath(dirname(__FILE__) . '/../application')); } Or even as a single statement: if(!defined('APPLICATION_PATH')) define('APPLICATION_PATH', realpath(dirname(__FILE__) . '/../application')); So why use the short-circuit code? Just for the 'coolness' factor of using logic operators in place of control structures? To consolidate nested if statements? Because it's faster?

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• OrientationEventListener not working properly

  - by nixau

  Hi all, I need to handle orientation changes in my Android application. For this purpose I decided to use OrientationEventListener convenience class. But his callback method is given somewhat strange behavior. My application starts in the portrait mode and then eventually switches to the lanscape one. I have some custom code executing in the callback onOrientationChanged method that provides some additional UI handling logic - it has a few calls to findViewById. What is strange is that when switching back from landscape to portrait mode onOrientationChanged callback is called twice, and what's even worse - the second call is dealing with bad Context - findViewById method starts returning null. These calls are made right from the MainThread @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); listener = new OrientationListener(); } @Override protected void onResume() { super.onResume(); // enabling listening listener.enable(); } @Override protected void onPause() { super.onPause(); // disabling listening listener.disable(); } I've replicated the same behavior with a dummy Activity without any logic except for one that deals with orientation hadling. I initiate orientation switch from the Android 2.2 emulator by pressing Ctrl+F11 What could be wrong? Upd: Inner class that implements OrientationEventListener private class OrientationListener extends OrientationEventListener { public OrientationL() { super(getBaseContext()); } @Override public void onOrientationChanged(int orientation) { toString(); } } }

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• Writing files in App_Data causes tempdata to be null

  - by RAMX

  I have a small asp.net MVC 1 web app that can store files and create directories in the App_Data directory. When the write operation succeeds, I add a message to the tempdata and do a redirectToRoute. The problem is that the tempdata is null when the action is executed. If i write the files in a directory outside of the web applications root directory, the tempdata is not null and everything works correctly. Any ideas why writing in the app_data seems to clear the tempdata ? edit: if DRS.Logic.Repository.Manager.CreateFile(path, hpf, comment) writes in the App_Data, TempData will be null in the action being redirected to. if it is a directory out of the web app root it is fine. No exceptions are being thrown. [AcceptVerbs(HttpVerbs.Post)] public ActionResult Create(int id, string path, FormCollection form) { ViewData["path"] = path; ViewData["id"] = id; HttpPostedFileBase hpf; string comment = form["FileComment"]; hpf = Request.Files["File"] as HttpPostedFileBase; if (hpf.ContentLength != 0) { DRS.Logic.Repository.Manager.CreateFile(path, hpf, comment); TempData["notification"] = "file was created"; return RedirectToRoute(new { controller = "File", action ="ViewDetails", id = id, path = path + Path.GetFileName(hpf.FileName) }); } else { TempData["notification"] = "No file were selected."; return View(); } }

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• How to inject a Session Bean into a Message Driven Bean?

  - by Hank

  Hi guys, I'm reasonably new to JEE, so this might be stupid.. bear with me pls :D I would like to inject a stateless session bean into a message-driven bean. Basically, the MDB gets a JMS message, then uses a session bean to perform the work. The session bean holds the business logic. Here's my Session Bean: @Stateless public class TestBean implements TestBeanRemote { public void doSomething() { // business logic goes here } } The matching interface: @Remote public interface TestBeanRemote { public void doSomething(); } Here's my MDB: @MessageDriven(mappedName = "jms/mvs.TestController", activationConfig = { @ActivationConfigProperty(propertyName = "acknowledgeMode", propertyValue = "Auto-acknowledge"), @ActivationConfigProperty(propertyName = "destinationType", propertyValue = "javax.jms.Queue") }) public class TestController implements MessageListener { @EJB private TestBean testBean; public TestController() { } public void onMessage(Message message) { testBean.doSomething(); } } So far, not rocket science, right? Unfortunately, when deploying this to glassfish v3, and sending a message to the appropriate JMS Queue, I get errors that glassfish is unable to locate the TestBean EJB: java.lang.IllegalStateException: Exception attempting to inject Remote ejb-ref name=mvs.test.TestController/testBean,Remote 3.x interface =mvs.test.TestBean,ejb-link=null,lookup=null,mappedName=,jndi-name=mvs.test.TestBean,refType=Session into class mvs.test.TestController Caused by: com.sun.enterprise.container.common.spi.util.InjectionException: Exception attempting to inject Remote ejb-ref name=mvs.test.TestController/testBean,Remote 3.x interface =mvs.test.TestBean,ejb-link=null,lookup=null,mappedName=,jndi-name=mvs.test.TestBean,refType=Session into class mvs.test.TestController Caused by: javax.naming.NamingException: Lookup failed for 'java:comp/env/mvs.test.TestController/testBean' in SerialContext [Root exception is javax.naming.NamingException: Exception resolving Ejb for 'Remote ejb-ref name=mvs.test.TestController/testBean,Remote 3.x interface =mvs.test.TestBean,ejb-link=null,lookup=null,mappedName=,jndi-name=mvs.test.TestBean,refType=Session' . Actual (possibly internal) Remote JNDI name used for lookup is 'mvs.test.TestBean#mvs.test.TestBean' [Root exception is javax.naming.NamingException: Lookup failed for 'mvs.test.TestBean#mvs.test.TestBean' in SerialContext [Root exception is javax.naming.NameNotFoundException: mvs.test.TestBean#mvs.test.TestBean not found]]] So my questions are: - is this the correct way of injecting a session bean into another bean (particularly a message driven bean)? - why is the naming lookup failing? Thanks for all your help! Cheers, Hank

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• Where should 'CreateMap' statements go?

  - by jonathanconway

  I frequently use AutoMapper to map Model (Domain) objects to ViewModel objects, which are then consumed by my Views, in a Model/View/View-Model pattern. This involves many 'Mapper.CreateMap' statements, which all must be executed, but must only be executed once in the lifecycle of the application. Technically, then, I should keep them all in a static method somewhere, which gets called from my Application_Start() method (this is an ASP.NET MVC application). However, it seems wrong to group a lot of different mapping concerns together in one central location. Especially when mapping code gets complex and involves formatting and other logic. Is there a better way to organize the mapping code so that it's kept close to the ViewModel that it concerns? (I came up with one idea - having a 'CreateMappings' method on each ViewModel, and in the BaseViewModel, calling this method on instantiation. However, since the method should only be called once in the application lifecycle, it needs some additional logic to cache a list of ViewModel types for which the CreateMappings method has been called, and then only call it when necessary, for ViewModels that aren't in that list.)

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• What's are the best readings to start using WPF instead of WinForms?

  - by Ivan

  Keeping in mind what CannibalSmith once said - "All the answers are saying "WPF is different". That's a huge understatement. You not only have to learn lots of new stuff - you must forget everything you've learned from Forms. It's a completely new way of doing UI." .. and having many years of experience with visual Windows desktop applications development (VB6, Borland C++ Builder VCL, WinForms) (which is hard to forget), how do I quickly move to developing to say well-formed WPF applications with Visual Studio? I don't need boozy-woozy graphics to give my app look and feel of a Hollywood blockbuster or a million dollar pyjamas. I always loved tidiness of standard Windows common controls and UI design guidelines, end even more I enjoyed them under Vista Glass Aero Graphite sauce. I am perfectly satisfied with WinForms but I want to my applications to be built of the most efficient and up-to-date standard technologies and architectured according to the most efficient and flexible patterns of today and tomorrow, leveraging interface-based integration and functionality reuse and to take all advantages of modern hardware and APIs to maximize performance, usability, reliability, maintainability, extensibility, etc. I very much like the idea of separating view, logic and data, letting a view to take all advantages of the platform (may it run as a web browser applet on a thin client or as a desktop application on a PC with a latest GPU), letting logic be reused, parallelized and seamlessly evolve, storing data in a well structured format in a right place. But... while moving from VB6 to Borland C++ Builder was very easy (no books/tutorials needed to turn it on and start working) (assuming I already knew C++), moving from BCB to WinForms was the same seamless, it does not seem any obvious to me how to do with WPF. So how do I best convert myself from a WinForms developer into a right-way thinking and doing WPF developer?

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• VB.Net Custom Object Master-Detail Data Binding

  - by clawson

  Since beginning to use VB.Net some years ago I have become slowly familiar with using the data binding features of .Net, however I often find my self bewildered by it's behavior and instead of discover the correct way it should work I find some dirty work around to suit my needs and continue on. Needless to say my problems continue to arise. I am using Custom Objects as the Data Sources for by controls and often entire forms. I find it frustrating to separate business logic and the graphical interface. (That could be a new question entirely.) So for a lot of objects I generate a form which has the DataBindingSource for the object. When I create each from using the New Constructor I explicitly pass to it the object to which it should be bound, and then set this passed object as the DataSource of the BindingSource. (That's a mouthful!) Now the Master object (say, bound to each form) often contains a List of objects which I like to have displayed in a DataGridView. I (sometimes) create and modify these child objects in their own form (again creating a databind the same way as the master form) but when I add them to the List in the master object the DataGridView won't update with the new items. So my question really has a few layers: How can I easily/efficiently/correctly update this DataGridView with the list of Detail objects when I add them to the list of the Master object. Is this approach to DataBinding good/viable. What's the best way to separate business logic from graphical interface. Thanks for the help!

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• Custom model validation of dependent properties using Data Annotations

  - by Darin Dimitrov

  Since now I've used the excellent FluentValidation library to validate my model classes. In web applications I use it in conjunction with the jquery.validate plugin to perform client side validation as well. One drawback is that much of the validation logic is repeated on the client side and is no longer centralized at a single place. For this reason I'm looking for an alternative. There are many examples out there showing the usage of data annotations to perform model validation. It looks very promising. One thing I couldn't find out is how to validate a property that depends on another property value. Let's take for example the following model: public class Event { [Required] public DateTime? StartDate { get; set; } [Required] public DateTime? EndDate { get; set; } } I would like to ensure that EndDate is greater than StartDate. I could write a custom validation attribute extending ValidationAttribute in order to perform custom validation logic. Unfortunately I couldn't find a way to obtain the model instance: public class CustomValidationAttribute : ValidationAttribute { public override bool IsValid(object value) { // value represents the property value on which this attribute is applied // but how to obtain the object instance to which this property belongs? return true; } } I found that the CustomValidationAttribute seems to do the job because it has this ValidationContext property that contains the object instance being validated. Unfortunately this attribute has been added only in .NET 4.0. So my question is: can I achieve the same functionality in .NET 3.5 SP1? UPDATE: It seems that FluentValidation already supports clientside validation and metadata in ASP.NET MVC 2. Still it would be good to know though if data annotations could be used to validate dependent properties.

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• Understanding how rpmbuild works

  - by ereOn

  Hi, For my work, I have to create a documentation on "How-to create a RPM package on Red Hat 5". I'm used to Debian and it's derivative (Ubuntu, and so on) and thus to Debian packages (aka. .deb files). It seems that the RPM logic is quite different from what I know already and I am having some issues understanding the "RPM logic". From what I read, it seems that ones need to be root to create a RPM package. While I understand why root could be required to install a package, I still don't understand why elevated privileges should be needed to just create one. If I try to create a RPM package as a user, changing the buildroot it fails on the %installstep because I don't have permission to write files into /usr/bin. Fair enough but... why does he want to copy my files into /usr/bin at this step ?! I just want to create the package, not install it ! I'm sure I'm missing something here. Is there anyone who could give me at least a basic understanding of how rpmbuild works and why ? Thank you very much !

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